The effects of nutritional strategies on body temperature of dairy cows are not well understood but could play an important role in adapting cows to changing climates. Cereal grains including wheat grain are rapidly degraded in the rumen while corn has a slower rate of fermentation. There is preliminary data that indicates there may be differences in body temperature between cows fed wheat or corn-grain. Twenty-four dairy cows were fed a diet that included either wheat grain (12 cows) or corn grain (12 cows) at 430 g/kg DM offered. Half the daily ration was offered at each of 06:00 and 15:00. At wk 4, 10 and 16 cows entered individual controlled-climate chambers at thermoneutral conditions for 48 h. Intravaginal temperature was recorded every 15 min using indwelling loggers. At wk 4, duration between afternoon feeding and maximum temperature tended (P < 0.10) to be longer for cows fed wheat (245 min) than cows fed corn (128 min). At wk 10, the maximum temperature after the morning feeding was lower (P < 0.05) in cows fed wheat (38.7°C) than cows fed corn (38.9°C). Cows fed wheat also had a lower minimum temperature than cows fed corn. After combining data across the entire experiment, the duration between feeding and maximum temperature was greater (P < 0.05) for cows fed wheat (230 min) than cows fed corn (155 min). Maximum temperature after the morning feeding was lower (P < 0.05) in cows fed wheat (38.6°) than cows fed corn (38.8°C). Daily minimum temperature was lower (P < 0.05) in cows fed wheat (38.0°C) than those fed corn (38.1°C). Reasons for these differences, which are in contrast to the ruminal degradation rates of wheat and corn, are unclear. In our previous research, acetate concentrations in the ruminal fluid of corn-fed cows have been greater than in wheat-fed cows. Diets that induce acetate fermentation in the rumen have previously been reported to increase body temperatures in cattle, and we speculate that this may have been the cause for the higher body temperatures of the corn-fed cows in this experiment. Irrespective of the mechanisms for the differences in body temperature, the feeding of different types of grains constitutes a potential nutritional strategy for ameliorating heat stress in dairy cattle.